Effect of erythrocyte mass on arterial blood pressure in dialysis patients receiving maintenance erythropoietin therapy

Abstract

Treatment of renal anemia with recombinant human erythropoietin (rEPO) frequently raises arterial blood pressure. The objective of this study was to determine whether this is a direct effect of rEPO or a consequence of the expansion of erythrocyte mass. Twenty-three chronic hemodialysis patients receiving maintenance rEPO therapy who had uncontrolled anemia due to iron deficiency were studied. It was anticipated that repletion of iron stores with iv iron dextran would restore rEPO responsiveness, leading to a gradual rise in hematocrit to the target values (0.30 to 0.33). The effect of the increase in hematocrit on arterial blood pressure could then be dissected from the direct effect of rEPO in patients receiving constant doses of rEPO throughout the study period. To this end, arterial blood pressure, iron indices, hematocrit, and measures of fluid balance were monitored at baseline and for a 10-wk period after iron repletion. In eight patients, the hematocrit transiently rose above 0.33, triggering a reduction in rEPO dosage. In the remaining 15 patients, rEPO dosage was held constant during the study period. In this subgroup, repletion of iron stores led to a rise in hematocrit from 0.25 ± 0.04 to 0.32 ± 0.04 (P<0.001) within 4 wk. Despite the significant rise in hematocrit, both systolic and diastolic blood pressure values remained virtually unchanged. Likewise, body weight and interdialytic fluid gain were unaltered. Furthermore, no patient required alteration in the type or dosage of antihypertensive medications during the observation period. In conclusion, a slow rise in hematocrit to the range of 0.30 to 0.33 in hemodialysis patients treated with constant doses of rEPO has no effect on arterial blood pressure. Thus, the effect of rEPO on arterial blood pressure does not appear to be related to the associated rise in erythrocyte mass within the limits of the hernatocrit values reached in this study.